With the number of Zika infections on the rise and real concerns of the virus spreading, governments are on the lookout for inventive ways to ramp up the response. These have included trials of experimental vaccines, trapping the bugs in junked tires and perhaps the most radical of all, using genetic engineering to kill off local mosquito populations. This strategy is beginning to gather some steam in the US, with federal regulators approving a field trial that would let engineered mosquitoes go to work in the state of Florida.

Humans have toyed with the idea of using genetic engineering to put the brakes on mosquito populations for years. These little critters are after all the single biggest threat to human life, spreading malaria, dengue and yellow fever to cause several million deaths each year and infect many millions more.

One of the main culprits behind this unmatched death toll is the Aedes aegypti, a mosquito found in tropical and subtropical regions that is the number one disease vector for dengue fever. Genetics researchers have targeted this innocuous killer through a number of approaches, looking to alter genes in ways that cause offspring to be born without wings, kill off their sense of smell and consign females to their birthplace for the entirety of their consequently shortened lives.

British company Oxitech has been a very active player in this field. In 2009 it released a bunch of its genetically modified mosquitoes on the Grand Cayman island in the Carribbean, killing off 80 percent of the local A. aegypti population. It has also conducted trials in Brazil and Panama, and has now been given the nod by the US Food and Drug Administration (FDA) to let its bug killers loose in Key Haven, Monroe Country, Florida.

Oxitech has engineered male mosquitoes, which don't bite humans or spread diseases, to possess a certain self-limiting gene. When these mosquitoes are released, they mate with wild female Aedes aegypti and this gene is passed along to the offspring. The gene is fatal for the babies and prevents them ever reaching adulthood.

Back in March, the FDA released a draft environmental assessment pertaining to the potential consequences of trialling Oxitech's mosquitoes in Key Haven. It has since received thousands of public comments and now published a final assessment, which concludes that the proposed field trial will have no "significant impacts on the environment."

While winning federal approval is an important step, it doesn't clear they way for Oxitech's mosquitoes to be used willy-nilly. They will still need to be approved by the Florida Keys Mosquito Control District, which is waiting on a referendum where locals will vote on whether releasing the genetically modified mosquitoes is really a good idea. This is set to take place in November, so we'll know more about a time-frame for the field trial if and when this final hurdle can be overcome.

GEORGE TOWN, Cayman Islands (AP) — The first wave of genetically modified mosquitoes were released Wednesday in the Cayman Islands as part of a new effort to control the insect that spreads Zika and other viruses, officials in the British Island territory said.

Genetically altered male mosquitoes, which don't bite but are expected to mate with females to produce offspring that die before reaching adulthood, were released in the West Bay area of Grand Cayman Island, according to a joint statement from the Cayman Islands Mosquito Research and Control Unit and British biotech firm Oxitec.

The mosquitoes will be released over nine months in an area known to be a hot spot for the Aedes aegypti species, which are not native to the Cayman Islands and are the main vector for Zika as well as other viruses, including chikingunya and dengue.

The project had been scheduled in June but the release was postponed first by a delay in getting an occupancy permit for the lab in which mosquitoes are bred and then by a court challenge from opponents who argued that the government had not provided sufficient information about potential risks or adequately studied other alternatives. A judge ruled Tuesday that the effort could proceed.

Oxitec has deployed its mosquitoes to fight Zika in Brazil following initial trials there and previously conducted tests in the Cayman Islands and Panama. Oxitec and officials in the Florida Keys have proposed testing there as well and are awaiting U.S. regulatory approval.

Oxitec Ltd., a British maker of genetically modified insects, plans to go door to door in coming weeks to pitch Key Haven, Fla., voters on the virtues of a modified mosquito that the company says can help kill off wild populations known to spread maladies like the Zika virus and dengue fever.

Critics of Oxitec’s proposed field trial are pushing back with yard signs and social-media campaigns, warning that the biotech mosquitoes aren’t needed to curb diseases and could harm local ecosystems.

The issue is dividing some of the about 1,000 citizens of Key Haven, an island community near Key West, where Oxitec and local pest-control officials are seeking federal permission for a trial release.

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What’s at Stake for U.S. GMOs?Study Sees Way to Limit Mosquitoes’ Ability to Spread ZikaU.S. Senate Nears Deal for Emergency Zika Virus FundingThe U.S. Food and Drug Administration, which is considering the proposed trial and gave it a preliminary nod in March, has received more than 2,600 comments arguing for and against the plan, and local meetings on the topic sometimes have devolved into shouting. In April, local officials decided to hold a public vote on the plan, scheduled for August.

“We’ll be trying to speak to every Key Haven resident we can,” said Derric Nimmo, Oxitec’s product development manager, who is leading public outreach in Florida. “The risk of Zika is very, very real. The risk of this technology is virtually nonexistent.”

ENLARGEBoth sides say much is at stake. The Florida Keys Mosquito Control District, which is working with Oxitec on the trial proposal, sees modified mosquitoes as a potential tool to curb the Aedes aegypti mosquito, an insect that has helped spread the Zika virus. Oxitec’s bugs are designed to pass along a gene that causes death in offspring before they reach adulthood, curbing the numbers of potentially infectious mosquitoes.

Last month, the U.S. Centers for Disease Control and Prevention confirmed that a 70-year-old Puerto Rican man in February died from Zika-related complications. The CDC has urged state and local agencies to prepare for Zika spreading in the U.S., particularly as the weather warms and more mosquitoes hatch.

For Oxitec, owned by Virginia-based biotechnology firm Intrexon Corp., the Florida trial may pave the way for a U.S. market that could reach $100 million in annual sales, according to financial services firm Wunderlich Securities Inc. Intrexon, which generated $174 million in sales last year, doesn’t disclose Oxitec’s revenue. The 14-year-old company emerged from Oxford University research into genetically modified bugs, and engineers moths and worms to cull cabbage- and cotton-munching pests.

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The Keys controversy has made Oxitec’s mosquitoes the latest proxy battle in an expanding U.S. debate over genetic engineering. A Vermont state law requiring labels for some food made from genetically modified crops has forced some food companies to apply such labels nationally.

Related VideoMosquitoes have an ugly track record of spreading everything from the Zika virus to dengue fever to malaria. Could they be killed off? Here's a short look at a controversial question.Pest-control officials chose Key Haven for the proposed trial because they say the small island community would clearly show whether Oxitec’s mosquitoes work. The company says its mosquitoes have killed more than 90% of wild Aedes aegypti populations in previous trials, roughly double the effectiveness of insecticides.

But Keys, situated along a 113-mile chain of bridges off Florida’s southern tip, also harbor a deeply independent streak.

“The people down here stick together when facing the government,” said Michael Doyle, executive director of the Key’s control district.

Opponents say the proposal represents government and corporate overreach that ignores residents’ concerns and could risk the Keys’ destination status for tourists. They say they are also worried about the potential impact on bats and frogs that consume Oxitec’s mosquitoes, and what may happen if female versions, which could bite people, are released.

‘We’re not willing subjects to be part of this experiment.’—Mila de Mier, Key Haven residentOxitec says the genes added to mosquitoes are nontoxic and nonallergenic for animals, and that Aedes aegypti mosquitoes aren’t a native Keys species and not a major food source for animals. The company estimates that less than 0.01% of all mosquitoes released are female and that any that do get released aren’t likely to live long enough to transmit Zika or dengue fever.

The FDA’s review, which included officials from the CDC and Environmental Protection Agency, found “negligible” environmental impacts, and in March the World Health Organization recommended testing Oxitec’s mosquitoes.

Mila de Mier, a real-estate agent who lives near the planned test site, says she initially liked the plan when she first heard about it four years ago. But she became wary when she perceived the Keys Mosquito Control District playing down locals’ concerns, she said.

“We’re not willing subjects to be part of this experiment,” said Ms. de Mier, who started an online petition against the plan and has gathered tens of thousands of signatures.

She said Oxitec should seek a different site where Zika or dengue are more pressing problems.